RIPEMD-160 (RIPE Message Digest) is a cryptographic hash function producing a 160-bit (20-byte) hash value. There are five functions in the family: RIPEMD, RIPEMD-128, RIPEMD-160, RIPEMD-256, and RIPEMD-320, of which RIPEMD-160 is the most common.

RIPEMD-160 is used in Bitcoin to compress SHA-256 hashed public keys into a shorter format as part of the process of generating Bitcoin addresses. This ensures that addresses are of a manageable length and maintains the cryptographic security of the Bitcoin network. 

The process is as follows:

First, a user's public key is hashed using SHA-256, resulting in a 256-bit hash. Next, this hash is processed using RIPEMD-160, which reduces it to a 160-bit hash. This step is crucial because it creates a shorter, more manageable hash.

The resulting RIPEMD-160 hash undergoes further processing and includes adding a version byte, creating a checksum through double SHA-256 hashing, and encoding it with Base58Check.

These steps together create the final Bitcoin address, which users can share to send and receive bitcoin.